An atraumatic case of extensive Achilles tendon ossification

•Achilles tendon ossification most often consists of focal lesions following trauma.•We present a case of atraumatic, near-total Achilles tendon ossification.•Surgical reconstruction that has not been utilized for this pathology is described.•This approach is a viable option and provided pain relief and return to function.

BackgroundOssification of the Achilles tendon is rare with most cases of ossification or calcification consisting of small, focal lesions. This pathology is usually predisposed by surgery, trauma, or other factors.Case descriptionA case of extensive Achilles ossification and calcification, without prior surgery or trauma, is reported. Following removal of one of the largest ossific masses reported in the literature, measuring 11.0 cm × 2.5 cm × 2.0 cm with additional 6.5 cm calcifications, surgical reconstruction was required.Purpose and clinical relevanceThe objective of this report was to describe an unusual case of Achilles tendon ossification and calcification that occurred without the presence of predisposing factors. When a large gap is present after removal of the ossification, direct repair may be impossible and V-Y lengthening plus flexor hallucis longus (FHL) transfer is a viable option for pain relief and return to function.